prevent_flutter.vhd

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--Prevent Flutter Module
--消抖模块
library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity Prevent_Flutter is
	port(
		clk : in std_logic;		--clock
		in1: in std_logic_vector(3 downto 0);		--input signal
		out1 : out std_logic_vector(3 downto 0)    --output signal
		);		
end Prevent_Flutter;

architecture code of Prevent_Flutter is
signal x,y:std_logic_vector(3 downto 0);
begin
	process(clk,x,y)
	begin
		if clk'event and clk='1' then
			for i in 0 to 3 loop
				x(i)<=in1(i);
				y(i)<=x(i);
			end loop;			
		end if;
		for j in 0 to 3 loop
			out1(j)<=x(j) or (not y(j));
		end loop;
	end process;
end code;